In recent years, an IP telephone system has been popularized which transmits and receives images and sound in the form of packet data bidirectionally in real time via an IP network. In the IP telephone system, not only can each of the server apparatuses connected to the IP network make an extension-to-extension call or an incoming or outgoing call, but also an extension-to-extension call or an incoming or outgoing call can be made between server apparatuses via the IP network.
In the IP telephone system, an IP telephone terminal function may have to be added or an unnecessary IP telephone terminal have to be removed according to the increase of personnel, a change of the business content, or the like in a department in which a server apparatus has been installed. In such a case, a conventional system has generally used a function providing method of incorporating functions beforehand and permitting a part or all of the functions to be used by inputting a license authentication code. In addition, it is common practice to place or lift restrictions on the use of functions in terms of capacity, such as the number of terminals that can use the functions or the memory capacity available in using a function, based on a license authentication code.
Furthermore, in the IP telephone system, IP telephone terminals are registered in individual server apparatuses on an IP network beforehand. When the user makes a call from his or her IP telephone terminal by use of an IP network, the server apparatus authenticates the license of an IP telephone terminal.
With the IP telephone system, to use an IP telephone terminal, the user must register the license of the terminal in a server apparatus. Therefore, in the IP telephone system using a redundant configuration of the server apparatuses, the user must register the license in an operating-system server apparatus and in a standby-system server separately in advance. In addition, it is necessary to prepare a third server apparatus to perform license authenticate without being affected by the driving situation of the operating system and standby system. Moreover, in the standby system, it is necessary to give unqualified approval to an IP telephone terminal that requests registration in the server.